Method for trimming programmable resistor to predetermined resistance

Abstract

A programmable resistor is an e-fuse connecting to a source/drain of a MOS transistor. A voltage is provided to the gate of the MOS transistor to partially blow the programmable resistor. Following that, a resistance comparator is used to compare the resistance of the programmable resistor to a predetermined resistance. If the resistance of the programmable resistor conforms to the predetermined resistance, then the programmable resistor is set. If it does not conform to the predetermined resistance, then it is determined whether partially blowing it again would make it exceed the predetermined resistance. If it will exceed the predetermined resistance, then it is not blown again. If it will not exceed the predetermined resistance, then the resistor is partially blown again so as to approach the predetermined resistance.

1. A method for trimming an electronic fuse (e-fuse), the e-fuse electrically connected to a doping zone of a transistor, the method comprising:
 providing a first gate voltage pulses to a gate of the transistor until the resistance of the e-fuse reaches a first predetermined resistance; and 
 providing a second gate voltage pulses to the gate of the transistor until the resistance of the e-fuse reaches a second predetermined resistance, the second predetermined resistance being larger than the first predetermined resistance; 
 wherein the e-fuse records at least two bits of data, and is used in a memory for recording data. 
 
   
   
     2. The method of  claim 1 , wherein the relation between the gate voltage and time is a square waveform. 
   
   
     3. The method of  claim 1 , wherein the e-fuse is reusable. 
   
   
     4. The method of  claim 1 , wherein the e-fuse is used as a programmable resistor. 
   
   
     5. The method of  claim 1 , wherein the transistor is a metal-oxide semiconductor (MOS) transistor.